19 Gastric Tumor Development in SMAD3-Deficient Mice Initiates From Forestomach/Glandular Transition Zone Along the Lesser Curvature

Abstract

Objective-SMAD proteins are downstream effectors of the TGF-β signaling pathway. Smad3 null mice develop colorectal cancer by 6 months of age. In this study, we have examined whether the loss of Smad3 promotes gastric neoplasia in mice.Design-The stomachs of Smad3 −/− mice were compared with age-matched Smad3 heterozygous and wild type mice. E-cadherin, Ki-67, phosphoSTAT3, and TFF2/SP expression was analyzed by immunohistochemisty. The shRNA-mediated knockdown of Smad3 in AGS and MKN28 cells was also performed. In addition, we examined alterations in DCLK1-expressing cells.Results-Smad3 −/− mouse stomachs at 6 months of age revealed the presence of exophytic growths along the lesser curvature in the proximal fundus. Six-month-old Smad3 −− mouse stomachs showed metaplastic columnar glands initiating from the transition zone junction between the forestomach and the glandular epithelium along the lesser curvature. Ten month-old Smad3 −/− mice all exhibited invasive gastric neoplastic changes with increased Ki-67, phosphoSTAT3 expression, and aberrant cytosolic E-cadherin staining in papillary glands within the invading submucosal gland. The shRNA-mediated knockdown of Smad3 in AGS and MKN28 cells promoted the expression of phosphoSTAT3. DCLK1-expressing cells, which also stained for the tuft cell marker acetylated-α-tubulin, were observed in 10-month-old Smad3 −/− mice within tumors and in fundic invasive lesions. Conclusion-Smad3